Visual discrimination of shape by humans

Reaction times to tachistoscopic exposure and a card-sorting task are the two methods by which visual discrimination of shape is studied. The results of experiments using both methods tally, i.e. the order of difficulty of the following shapes was: (1) (easiest) circle vs. triangle; (2) circle vs. square; (3) square vs. triangle; (4) (most difficult) triangle vs. diamond. These results are compared with those obtained by Sutherland, using octopus, and it is concluded that it should be possible to establish to what extent the system of visual analysis in humans differs from that postulated for both octopus and rat.     

Appetitive behavior, compulsivity, and neurochemistry in Prader-Willi syndrome

Advances in genetic research have led to an increased understanding of genotype-phenotype relationships. Excessive eating and weight gain characteristic of Prader-Willi syndrome (PWS) have been the understandable focus of much of the research. The intense preoccupation with food, lack of satiation, and incessant food seeking are among the most striking features of PWS. It has become increasingly clear that the behavioral phenotype of PWS also includes symptoms similar to obsessive compulsive disorder, which in all probability interact with the incessant hunger and lack of satiation to engender the intense preoccupation and food seeking behavior that is characteristic of this disorder. Several lines of evidence suggest that genetic material on chromosome 15 may alter synthesis, release, metabolism, binding, intrinsic activity, or reuptake of specific neurotransmitters, or alter the receptor numbers and/or distribution involved in modulating feeding. Among the likely candidates are GABAnergic, serotonergic, and neuropeptidergic mechanisms. This review summarizes what is known about the appetitive behavior and compulsivity in PWS and discusses the possible mechanisms underlying these behaviors. MRDD Research Reviews 2000;6:125-130.     

Gender differences in responses to depressed mood in a college sample

Two studies tested the hypothesis that women are more likely than men to focus on themselves and their mood when in a depressed mood, and that this leads them to experience longer periods of depressed mood. In both studies subjects were predominantly Caucasian college students. In our first study, a laboratory study, females chose to engage in an emotion-related task significantly more often than did males, even when this lead them to focus on an existing sad mood. In the second study, a prospective naturalistic study, females were more likely than males to evince an emotion-focused ruminative style of coping with their moods. A ruminative response style at Time 1 was a significant predictor of depression scores at Time 2, even after initial levels of depressed mood were taken into account. Furthermore, once rumination levels were controlled for, gender was no longer a potent predictor of depression outcome. The implications of these response styles for treatment are discussed.We thank Brandi Battistoni, Kim Bergquist, Rachel Carr, Lisa Lougee, and especially Ariel Lang for their invaluable help in data collection. We also thank Chuck Olson, Jannay Morrow, and Rose McDermott for their helpful comments on earlier drafts.     

The Effects of Gender on Career Decision Problems in Young Adults

The authors investigated gender differences in psychological problems in the career decision making (CDM) process of young adults. Specifically, problems with decision anxiety, life-goal awareness, luck-fate orientation, authority orientation, and secondary gain motivation were investigated. Methodology involved administering the Career Decision Diagnostic Assessment (CDDA) instrument to 1,006 college students from four universities. Results indicated no gender differences in global levels of problems in CDM. Women reported more problems with life-goal awareness and authority orientation than did men. Men reported more problems with secondary gain motivations than did women. The results are discussed in terms of implications for gender-differentiated career counseling.     

Expectancies of reinforcer location and quality as cues for a conditional discrimination in pigeons

Experiment 1 demonstrated that reliably correlating different reinforcer locations (top vs. bottom) with sample stimuli markedly enhanced the performance of White Carneaux pigeons in a spatial conditional discrimination. This differential outcome effect was more evident at longer retention intervals. In Experiment 2, pigeons were given the opportunity to learn about two redundant reinforcer features--location (top vs. bottom) and quality (grain vs. chow). Which reinforcer feature exerted control over choosing depended on task structure. In the congruent task, where pecks to the top key operated the top feeder and pecks to the bottom key operated the bottom feeder, reinforcer location exerted predominant control. In the incongruent task, where pecks to the top key operated the bottom feeder and vice versa, reinforcer quality exerted exclusive control. These results have implications for the nature of reinforcer representations in instrumental learning.     

Food, mood, and attitude: reducing risk for eating disorders in college women.

Food, Mood, and Attitude (FMA) is a CD-ROM prevention program developed to decrease risk for eating disorders in college women. Female 1st-year students (N = 240) were randomly assigned to the intervention (FMA) or control group. Equal numbers of students at risk and of low risk for developing an eating disorder were assigned to each condition. Participants in the FMA condition improved on all measures relative to controls. Significant 3-way interactions (Time x Condition x Risk Status) were found on measures of internalization of sociocultural attitudes about thinness, shape concerns, and weight concerns, indicating that at-risk participants in the intervention group improved to a greater extent than did low-risk participants. At follow-up, significantly fewer women in the FMA group reported overeating and excessive exercise relative to controls.     

Inattentional blindness for ignored words: Comparison of explicit and implicit memory tasks

Inattentional blindness is described as the failure to perceive a supra-threshold stimulus when attention is directed away from that stimulus. Based on performance on an explicit recognition memory test and concurrent functional imaging data Rees, Russell, Frith, and Driver [Rees, G., Russell, C., Frith, C. D., & Driver, J. (1999). Inattentional blindness versus inattentional amnesia for fixated but ignored words. Science, 286, 2504–2507] reported inattentional blindness for word stimuli that were fixated but ignored. The present study examined both explicit and implicit memory for fixated but ignored words using a selective-attention task in which overlapping picture/word stimuli were presented at fixation. No explicit awareness of the unattended words was apparent on a recognition memory test. Analysis of an implicit memory task, however, indicated that unattended words were perceived at a perceptual level. Thus, the selective-attention task did not result in perfect filtering as suggested by Rees et al. While there was no evidence of conscious perception, subjects were not blind to the implicit perceptual properties of fixated but ignored words.     

Fixation identification in centroid versus start-point modes using eye-tracking data

Fixation-identification algorithms, needed for analyses of eye movements, may typically be separated into three categories, viz. (i) velocity-based algorithms, (ii) area-based algorithms, and (iii) dispersion-based algorithms. Dispersion-based algorithms are commonly used but this application introduces some difficulties, one being optimization. Basically, there are two modes to reach this goal of optimization, viz., the start-point mode and the centroid mode. The aim of the present study was to compare and evaluate these two dispersion-based algorithms. Manual inspections were made of 1,400 fixations in each mode. Odds ratios showed that by using the centroid mode for fixation detection, a valid fixation is 2.86 times more likely to be identified than by using the start-point mode. Moreover, the algorithm based on centroid mode dispersion showed a good interpretation speed, accuracy, robustness, and ease of implementation, as well as adequate parameter settings.     

Non-lateralised deficits of drawing production in hemispatial neglect

Spatially lateralised deficits that typically define the hemispatial neglect syndrome have been shown to co-occur with other non-lateralised deficits of attention, memory, and drawing. However even a simple graphic task involves multiple planning components, including the specification of drawing start position and drawing direction. In order to investigate the influence of these factors in neglect we presented patients with a circle-copying task, and specified the drawing start point. The ability to draw from the instructed location was strongly related to tests that measure constructional abilities, but not related to start point laterality. In contrast, the direction in which patients drew the circle was affected by start point laterality: patients with neglect were less likely to draw in a typical direction when the cue was on the affected side of space and this was strongly related to severity of the neglect. Patients with neglect consistently produced circles that were smaller than the model; however, the scaling was not affected by the laterality of the start point, nor was the proportion of drawings correctly started at the cue. These findings demonstrate the complex relationship between neglect and even the simplest test for the syndrome.